The present invention relates to an arrangement for controlling in a motor vehicle an automatically shifting transmission driven by an internal-combustion engine and controlled electrohydraulically, the engine being influenced by means of a power control element, such as an accelerator pedal or a throttle valve, and gear positions of the transmission, by at least two shifting programs optimized according to different design criteria, the transmission being automatically shiftable at least as a function of the position of the throttle valve and of the rotational speed of the engine. The shifting programs are manually selectable by the driver or automatically selectable by a change-over strategy as a function of operating or driving parameters.
An electrohydraulically controlled, automatically shifting transmission is described in Bosch "Technische Berichte", (7/1983)4; Pages 160 to 166, and ATZ 85 (1983)6, Pages 401 to 406. This transmission has two shifting programs for the automatic shifting of the gear positions of the transmission which are optimized according to two different design criteria. By means of a switch, the driver of a vehicle may select either a power-optimized or a consumption-optimized shifting program.
German Patent Document DE-33 41 652 C2 and German Patent Document DE 39 22 051.6, which is not a prior publication, show a transmission control system in which the shifting programs are selected automatically by a change-over strategy which is a function of operating or driving parameters. These transmission control systems, for example, by sensing and analyzing accelerator pedal or throttle valve signal values, generate a quantity which is a measurement for a driving style or a driving method of the driver of the motor vehicle. On the basis of this quantity, the transmission control system selects a shifting program which corresponds to the driver's driving method from several shifting programs ranging from a purely consumption-optimized to a purely power-optimized shifting program.
A problem arises if a motor vehicle having such an automatically shifting transmission which is operated by change-over shifting programs, after a cold start of the internal-combustion engine, is driven by the consumption-optimized shifting program for an extended period of time. (In the case of the two last-mentioned transmission control systems this may frequently occur as a result of the advised quick handling with a still cold internal-combustion engine). It was found that as a result of the consumption-optimized operating mode of the motor vehicle, an emission control system which is connected behind the internal-combustion engine and also the internal-combustion engine itself does not reach its operating temperature for an extended period of time. However, particularly in the case of emission control systems, a fast reaching of the operating temperature is extremely important in order to achieve a high pollutant conversion rate.
An object of the present invention is to provide a motor vehicle having an automatically shifting transmission which is driven by an internal-combustion engine, is preferably electrohydraulically controlled and in which the internal-combustion engine and an emission control system connected behind it reach an operating temperature required for a good functioning relatively rapidly.
This and other objects are achieved by the present invention which provides an arrangement for controlling in a motor vehicle an automatically shifting transmission driven by an internal-combustion engine and controlled electrohydraulically. The engine is controllable by a throttle valve and gear positions of the transmission, the transmission being automatically shifted as a function of a position of the throttle valve and a rotational speed of the engine. The arrangement comprises a means for sensing a cold-start condition of the motor vehicle, and a transmission control unit coupled to the means for sensing. This transmission control unit shifts the gear positions of a transmission according to one of at least two shifting programs optimized according to different design criteria. One of the shifting programs is a consumption-optimized shifting program and another of the shifting programs is a warmup shifting program, with the shifting programs being manually selectable by a driver of the motor vehicle or automatically selectable by a change-over strategy as a function of operating or driving parameters. The transmission control unit, as a function of a sensed cold-start condition, shifts the gear positions for at least a limited time period according to the warmup shifting program such that the engine under identical driving conditions generates higher exhaust gas mass or exhaust gas energy flows than for gear positions shifted according to the consumption-optimized shifting program.
An advantage of the present invention is that a motor vehicle is provided which has an automatically shifting transmission which is driven by an internal-combustion engine, is preferably controlled electrohydraulically and in which the internal-combustion engine and an emission control system connected behind it relatively rapidly reach an operating temperature important for their proper functioning without any noticeably increased fuel consumption.
The present invention is easy to implement because it requires only a temperature signal of a corresponding temperature sensor which, as a rule, is normally sensed in motor vehicles and is otherwise limited to a slight expansion of a control program of the transmission control system.
An embodiment of the present invention provides that a cold-start condition of the motor vehicle is sensed by means of the temperature sensor, on the basis of which a transmission control system, at least for a limited time period, shifts the gear positions by means of a specific shifting program in such a manner that, under the same driving conditions, the internal-combustion engine generates higher exhaust gas mass flows or exhaust gas energy flows than in the case of the gear positions shifted by means of a consumption-optimized shifting program.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.